Fifty women with unexplained infertility will undergo hysteroscopy and directed biopsy of selected areas of the endometrium between days 20 and 22 of the menstrual cycle. Timing will be verified by a correlation with a BBT and LH peak. In addition, endometrial samples will be obtained utilizing a small aspiration biopsy curette. These tissue samples will be analyzed for estradiol and progesterone receptor content and histologic pattern. The findings will be correlated with the concentration of estradiol and progesterone in peripheral serum. This study is designed to assess the role of hysteroscopy in the investigation of unexplained infertility, the frequency of steroid receptor dysfunction in unexplained infertility and the ability of blind endometrial biopsy techniques to accurately sample selected areas for receptor analysis.